The present invention relates to a method of correcting photometric conditions for a photographic film.
FIG. 1 shows the conventional method to determine exposure conditions when picture frames of a photographic film are scanned so that photometric values are analyzed to obtain appropriate prints. The prior art comprises taking a picture of an object 1 on a film 2, photometrically measuring 4 the film at the stage of development process 3, analyzing 5 the object 1 and estimating a picture image of the object 1 from the result of the analysis 5 thereof for determination of exposure conditions. In the prior art, however, it is difficult to discriminate whether the result of the analysis is attributable to the object 1 itself or to the fluctuation at the stages of the film 2 and the development process 3 as the data related to the fluctuation in the film 2 as well as the development process 3 is outputted, too, even though the analysis on the object 1 itself is conducted at the analyzing stage 5.
There has never been proposed any effective method to correct photometric conditions in order to solve such problems. There has been proposed a method (Japanese Patent Laid-open No. 13333/1977) of adjusting directly an exposure control unit which comprises photographing an illumination light source in advance between one picture frame and another, and controlling the printing conditions by making the location a predetermined color. Since the light source photographed on the film according to this method is not the light source to illuminate the object but includes reflected light from the background, the method is not very satisfactory in precision although it has a higher precision compared to the method using average density of the whole film area. Another method (e.g. Japanese Patent Laid-open No. 129335/1980) has been proposed which exposes a predetermined color synthetic mark on an unexposed location of a film before development in order to identify the type of the film and measures it with a 6-color filter. But this method is defective in that the equipments unavoidably become very complex and the measuring operation is extremely difficult.